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

my $in_file  = 'input.txt';
my $out_file = 'output.txt';
my @result;

open my $handle_in, '<', $in_file or die "$in_file: $!";

while ( <$handle_in> ) {
	# split (into 2 parts) at = (enclosed in optional whitespaces)
	# use the last part and store it in @result
	push @result, ( split( /\s*=\s*/, $_, 2 ) )[-1];
}

close $handle_in;

# remove line breaks from array elements
chomp @result;

open my $handle_out, '>', $out_file or die "$out_file: $!";

# print elements (ignore undefined and empty ones)
print $handle_out join( '/', grep { defined && length > 0 } @result )
  or die "$out_file: $!";

close $handle_out or die "$out_file: $!";

__END__