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

my $filename = __FILE__;

my %offset_type = ( number    => 1,
                    string    => 'abc',
                    reference => { a => 23 },
                    object    => bless do { \ my $object }, 'Class'
                  );


for my $type (keys %offset_type) {
    my $offset = $offset_type{$type};
    open my $FH, '<', $filename or die $!;
    eval {
        warn "$type without quotes\n";
        seek $FH, $offset, 0 or die "Report error - $!";
        warn "quoted $type\n";
        seek "$FH", $offset, 0 or die "Report error - $!";
    1 } or warn $@;
}
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Update: Adding output:

number without quotes
quoted number
seek() on unopened filehandle at ./1.pl line 21.
Report error - Bad file descriptor at ./1.pl line 21.
reference without quotes
quoted reference
seek() on unopened filehandle at ./1.pl line 21.
Report error - Bad file descriptor at ./1.pl line 21.
string without quotes
Argument "abc" isn't numeric in seek at ./1.pl line 19.
quoted string
seek() on unopened filehandle at ./1.pl line 21.
Report error - Bad file descriptor at ./1.pl line 21.
object without quotes
quoted object
seek() on unopened filehandle at ./1.pl line 21.
Report error - Bad file descriptor at ./1.pl line 21.
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Please, read Short, Self Contained, Correct Example on how to post helpful code.

If you need to check whether something is a number, use Scalar::Util's looks_like_number.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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