. is for string concatenation (see Additive operators), = is an assignment operator.

my $messageText = "This is some text\n";
$messageText .= "Add more text here\n";

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Is the same as:

my $messageText = "This is some text\n";
$messageText = $messageText . "Add more text here\n";

[download]

Update: added brackets to link, fixed typo

In reply to Re: What does ".=" mean? by marto
in thread What does ".=" mean? by anaconda_wly

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