I think a better way to recursively process all files would be to pass your processing subroutine as a code reference to File::Find.

use warnings;
use strict;
use File::Find

my $curUrl = "http://localhost:8080";
my $tarUrl = "http://localhost";

sub process_files
{
    next unless -f $File::Find::name;

    print "Processing $File::Find::name\n";

    open FILE, "+>", $File::Find::name
        or die "Could not open file $File::Find::name";

    while (my $line = <FILE>) {
        $line =~ s/$curUrl/$tarUrl/g;
    }
    close FILE;
}

find( &process_files, $ARGV[0] );
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It is a bit old school perl, but sometimes I find the old tools are the best.