If your input is somehow fixed in it's content the easiest thing is using the flip-flop operator (see flip flop at my library and in perlop):

while (<DATA>){
    print if /SCHEDULE "DUMMY CHECK"/ .. /INTERVAL/;
}
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If you just want to print 3 lines after a match (but notice you have empty lines that count! i used 6 lines..) you can use or a count, as you already have done, or use the special variable $. (explained in perlvar ) that is line number:

my $switch;
while (<DATA>){
    $switch = $. if /SCHEDULE "DUMMY CHECK"/;
    if ( $switch and $. <= $switch + 6){
        print;
    }
}
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As final note @data = $_; does not make muche sense for me: you want to split the line? dont forget also to chomp

L*