Regex and the characters case

Okay, I got a rather simple one (at least seems simple). I have a multi lined string and I am just playing around with replacing different words with something else. Let me show you...

#!/usr/bin/perl -w
use strict;

$_ = "That is my coat.\nCoats are very expensive.";
s/coat/Hat/igm;
print;

The output would be

That is my Hat

Hats are very expensive...

The "hat" on the first line shouldn't be capitalized. Are there any tricks that can make the casing开发者_开发百科 compliant with how english is written? Thanks :)

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see how-to-replace-string-and-preserve-its-uppercase-lowercase

For more detail go to How do I substitute case insensitively on the LHS while preserving case on the RHS?

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You can use the e modifier to s/// to do the trick:

s/(coat)/ucfirst($1) eq $1 ? 'Hat' : 'hat'/igme;

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For one, you should use \b (word boundary) to match only the whole word. For example s/hat/coat/ would change That to Tcoat without leading \b. Now for your question. With the flag /e you can use Perl code in the replacement part of the regex. So you can write a Perl function that checks the case of the match and then set the case of the replacement properly:

my $s = "That is my coat.\nCoats are very expensive.";
$s =~ s/(\bcoat)/&same_case($1, "hat")/igme;
print $s, "\n";

sub same_case {
        my ($match, $replacement) = @_;

        # if match starts with uppercase character, apply ucfirst to replacement
        if($match =~ /^[A-Z]/) {
                return ucfirst($replacement);
        }
        else {
                return $replacement;
        }
}

Prints:

That is my hat.
Hats are very expensive.

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This may solve your problem:

#!/usr/bin/perl -w

use strict;

sub smartSubstitute {
    my $target = shift;
    my $pattern = shift;
    my $replacement = shift;

    $pattern = ucfirst $pattern;
    $replacement = ucfirst $replacement;

    $target =~ s/$pattern/$replacement/gm;

    $pattern = lcfirst $pattern;
    $replacement = lcfirst $replacement;

    $target =~ s/$pattern/$replacement/gm;

    return $target;
}

my $x = "That is my coat.\nCoats are very expansive.";
my $y = smartSubstitute($x, "coat", "Hat");
print $y, "\n";