About issue of chomp command

what 's the issue?

   chomp function can't assign to others variable.

for example:
# cat /tmp/a
a
d
g
f

# cat /tmp/b.pl

 

#!/usr/bin/perl
$file="/tmp/a";
@array=qw(a b c d);
open(FH,"$file") or die "couldn't open $file:$!";
foreach (<FH>) {
        $line=chomp($_);

        print "$line\n";
        foreach (@array) {
                $item=chomp($_);
                if ("$item" eq "$line" ){
                print "$line\n";
                }
        }
}


resulut:
1
1
1
1

what's the root cause?

   

#!/usr/bin/perl
$file="/tmp/a";
@array=qw(a b c d);
open(FH,"$file") or die "couldn't open $file:$!";
foreach () {
        chomp;
        $line = $_;
        foreach (@array) {
                chomp;
                $item=$_;
                if ("$item" eq "$line" ){
                print "$line\n";
                }
        }
}

note: The result of chomp can't assign to other variable

      $line = chomp($_);    #return value will be 1