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

my $found = 0;

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

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

No need to add a loop:

use Modern::Perl;
my $gen_build_man = 'C:\python.py';
open my $GENMAN, '<', $gen_build_man or die "could not open $gen_build
+_man - $!"; 
{
    local $/=undef;
    my $file = <$GENMAN>;    
    say 'genman.pl not found in the file' unless $file =~ /genman\.pl/
+;
}
[download]

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

My blog: Imperial Deltronics