#!/usr/bin/perl

use strict;
use warnings;

my $loop_line = "static replace [something] and [another] thing";

my @matches = $loop_line =~/\[(.*)\]/; # Build a list of matches
for ( @matches ) {
    $loop_line =~ s/\Q$_\E/PING/;
}

print $loop_line, "\n";

__END__
static replace [PING] thing