You can add -n to the first line of your script and set all needed variables in the BEGIN{} block (which is not looped like all other code when using -n):

#!/usr/bin/perl -wn
BEGIN{
 use strict;
 my $outFile= "output.txt";
 my $inFile= "infile.txt";
 $main::start=17; # 'my' in this scope will result in uninitialized va
+lues outside the BEGIN{} block
 $main::end=30;
 close STDOUT; close STDIN;
 open STDIN,"<",$inFile || die $!;
 open STDOUT,">",$outFile || die $!;
}
print if $. >= $start && $. <= $end;
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