As above, check your (implicit open) in line 3.

Nonetheless, your script (with its numerous problems intact) reads the spreadsheet au.xls (when that's in same dir with the script and presumably, when au.xls actually exists where you say it does.

au.xls, in same dir with script:

captionColA                captionColB    captionColC
http://abc.com            3            abc
http://www.xyz.com        4            xyz
foo.bar                    5            fb
[download]

and, changing your test in line 12 to if ($row > 0) { (still not the right way to do this, but workable), execution looks like this:

pl_test>perl 827414.pl
http://abc.com
http://www.xyz.com
foo.bar
Use of uninitialized value in foreach loop entry at 827414.pl line 12.
Use of uninitialized value in foreach loop entry at 827414.pl line 12.
Argument "" isn't numeric in numeric gt (>) at 827414.pl line 14.
Use of uninitialized value in foreach loop entry at 827414.pl line 12.
Use of uninitialized value in foreach loop entry at 827414.pl line 12.
Argument "" isn't numeric in numeric gt (>) at 827414.pl line 14.

pl_test>
[download]

And the minimally-modified (ie, largely uncorrected) script:

#!/usr/bin/perl
use strict;
use warnings;
# id: 827414

use Spreadsheet::ParseExcel;    
my $excel = Spreadsheet::ParseExcel::Workbook->Parse("au.xls");
my $excel_file_url;
#start looping the Excel sheet
for my $sheet (@{$excel->{Worksheet}}) {
    $sheet->{MaxRow} ||= $sheet->{MinRow};
    for my $row ($sheet->{MinRow} .. $sheet->{MaxRow}) {
        #looping for each row
        if ($row > 0) {
            #get the file url path from excel sheet at  corresponding 
+row, col 0
            my $cell_value=$sheet->{Cells}[$row][0];
            $excel_file_url=$cell_value->{Val};
            print $excel_file_url . " \n";
        }
   }
}
[download]

HTH.