use strict;
use warnings;
my $gen_build_man = C:\python.py
open my $GENMAN, '<', "$gen_build_man" or die "could not open $gen_build_man - $!"; 

my $found = 0;

while ( my $line = <$GENMAN> ){
    $found = 1 if $line =~ /genman\.pl/;
}

print "genman.pl not found in the file" if ! $found;