I like the flip-flop operator as demo'd by Discipulus. If I don't use that, I often use the following pattern. The flip-flop operator maintains the state of whether you are inside the record or not - that's a very nice feature. Anyway, without the flip-flop, instead of maintaining a flag to tell me if I'm in the record or not, I call a subroutine to keep track of the "state". This may be a bit "wordy", but the logic is crystal clear (at least to me).

#!/usr/bin/perl
use strict;
use warnings;

while (defined (my $line = <DATA>))
{
   process_record($line) if $line =~ /^\s*SCHEDULE "DUMMY CHECK"/;
}


sub process_record
{
   my $line = shift;  #the "trigger line"
   print $line; 
   
   for (1..3)  #maybe have regex for "end of record"?
   {
      my $line = <DATA>;
      print $line;
   }
   print "\n";  #just a spacer
}

=prints
SCHEDULE "DUMMY CHECK"
DESCRIPTION "Do some stuff"
Check something
INTERVAL "10m"

SCHEDULE "DUMMY CHECK"
DESCRIPTION "Do some more stuff"
Check something
INTERVAL "30m"
=cut

__DATA__
SCHEDULE "TEST"
DESCRIPTION "Do Some stuff"
MINUTE "53"
HOUR "21"
SCHEDULE "DUMMY CHECK"
DESCRIPTION "Do some stuff"
Check something
INTERVAL "10m"
MINUTE "50"
HOUR "21"
SCHEDULE "TEST"
DESCRIPTION "Do Some stuff"
MINUTE "53"
HOUR "21"
SCHEDULE "DUMMY CHECK"
DESCRIPTION "Do some more stuff"
Check something
INTERVAL "30m"
MINUTE "50"
HOUR "21"
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