Dominating the entire game, it took until two minutes into the second half for Boro to make the breakthrough when Parrett fired home from Pett's cross. Chris Day was a virtual spectator throughout as the Cumbrians offered little threat, but Carlisle could still have spoiled Boro's party had they not missed a golden chance to equalise on the hour.
Tom Conlon and Dave Martin returned to the Stevenage starting XI for this one, with Simon Walton dropping to the bench to be joined by the returning Ben Kennedy and Jack Jebb among others.
Stevenage knew a win would guarantee themselves a playoff spot and straight from the off Boro were out of the blocks, with Chris Beardsley closing down a clearance within second and then Tom Conlon inches away from meeting a Dave Martin cross from the right.
It was to set the tone for an opening 45 minutes of dominance by the hosts, who set up with Chris Whelpdale at right-back and Andy Bond in midfield with Conlon bursting forward to support Beardsley.
A whole host of early corners put the pressure on visitors Carlisle in the opening 10 minutes but aside from a Bond shot which deflected behind, but was oddly given as a goal-kick, the visiting defence stood firm.
Whelpdale was to have plenty at joy on the right-flank, advancing seemingly unopposed at times and one such move on 11 minutes saw the winger reach the edge of the box and fire low, straight at Gillespie.
Bar the odd venture forward Carlisle seemed completely reluctant to push into the Boro half, simply inviting the hosts onto them as Stevenage constantly probed looking for the breakthrough. Conlon fired over from 30 yards and Whelpdale found the side netting after cutting inside, as chances came and went around the half hour mark with Boro again racking up the corners.
Five minutes before the break a superb interchange of passes between Whelpdale, Conlon and Beardsley saw Conlon slide in Beardo, with the striker’s shot blocked behind. Had it gone in it would have been a magnificent team goal.
Whelpdale continued to catch the eye in the closing moments of the half, twisting past the midfield and forcing Gillespie to tip a low effort around the post at full stretch. Moments later, his near post flick wide from a late Martin corner concluded the opening half’s actions.
If the first half was one of frustration for the hosts, the second began in perfect style as Boro took the lead just two minutes after the restart. Stevenage pushed forward and when Pett cut the ball back to the edge of the area, there was Dean Parrett to fire home.
It looked set to spark another avalanche of pressure as Boro again pushed forward with the visitors content to sit back. Conlon tested Gillespie from range for a second time, Pett saw a shot blocked on the counter and Whelpdale again fired over as the hosts kept up the momentum.
However for all their dominance Graham Westley’s men were given a big let-off as Carlisle should have equalised on the hour. From a Carlisle counter-attack Mark Beck broke free and his inviting ball across could only be poked wide by Brad Potts when it looked easier to score.
Beck himself nodded wide under pressure from Day as the Cumbrians again ventured forward before Boro won back momentum with subs Bruno Andrade and Ben Kennedy giving Boro new life up top.
Parrett went close to a second with a deflected effort and then with 13 minutes remaining Boro thought they’d doubled their advantage when Pett smashed an effort off the far post, but the ball bounced clear.
Half-chances came and went as both sides pushed in the final stages but, with the crowd buoyed by a late winner for Southend against Luton, Graham Westley’s men saw out the last minutes and will now prepare for the playoffs with a tricky trip to Kenilworth Road next Saturday.
Stevenage: Day, Whelpdale, Wells, Dembele, Okimo, Bond, Conlon (Andrade 58), Parrett (Jebb 90), Pett, Martin (Kennedy 66), Beardsley
Subs not used: Beasant, Henry, Deacon, Walton
Carlisle: Gillespie, Grainger, Kennedy, Potts, Brough, Dempsey, O’Hanlon, Wyke (Beck 4), Young (Dicker 77), Griffith (Rigg 55), Atkinson
Subs not used: Hanford, Buddle, Thirlwell, Paynter
Referee: Darren Drysdale
Attendance: 3,632 (478 away)