perl not going to error path

[gupr1980]

I have a perl script

open my $file, '<', $filename or die $!;
seek $file, $offset, 0 or die "Report error - $!";

when I pass a non numeric offset, the perl script errors out but it doesn't seem to go to the die section. It does not print the "Report error ... message. I got a tip from another forum to add a quote around the file handle of the seek command http://stackoverflow.com/questions/34964638/perl-doesnt-go-to-error-section

seek "$file" blah blah

this works and now the perl goes to die and prints the error message. I don't understand why this quote was necessary. Please explain if you can. thanks for your time.