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

# runs through all lines from STDIN or ARGV files
while (<>) {
    $_ = search_and_replace( $_, \&log_if_replaced );
    print;
}

# Try each replacement, in order, and call the trigger with the result
# and return the (possibly modified) text
sub search_and_replace {
    my $text = shift; # the text
    my $trigger = shift; # optional subref to handle matches

    foreach ( search_and_replace_operations() ) {
        my ($pattern, $replacement) = @{ $_ };

        my $matched; # did it match or not?
        $matched = $text =~ s{$pattern}{$replacement}g;

        $trigger->($matched, $text, $pattern, $replacement)
           if $trigger;
    }

    return $text;
}

# the replacements... (could be read from a file, etc)
sub search_and_replace_operations {
    return (
    [ qr/searchregexp1/, 'replacementstring1' ],
    [ qr/[0-9]+/, 'I am not a number' ],
    # etc
    [ qr/\s+$/, "\n" ], # standardize whitespace at end
    );
}

# this trigger gets called for every match attempt
# and logs a message for every replacement.
sub log_if_replaced {
    my $matched = shift;
    my $text = shift;
    my $pattern = shift;
    my $replacement = shift;

    foreach ($text, $pattern, $replacement) {
        # escape whitespace for readable logs
        s{([\s])}{ escape_whitespace($1) }ge;
    }

    print STDERR "'$pattern' -> '$replacement' result: '$text'\n"
        if $matched;
};

# make whitespace readable for logs
sub escape_whitespace {
    my $char = shift;

    return ' ' if $char eq " ";
    return '\n' if $char eq "\n";
    return '\t' if $char eq "\t";

    return '\x{' . (ord($char)) .'}';
}