If I had:
$foo= "12."bar bar bar"|three";
how would I insert in the text ".." after the text 12. in the variable?
Perl allows you to choose your own quote delimiters. If you find you need to use a double quote inside of an interpolating string (i.e.
"") or single quote inside of a non-interpolating string (i.e.
'') you can use a quote operator to specify a different character to act as the delimiter for the string. Delimiters come in two forms: bracketed and unbracketed. Bracketed delimiters have different beginning and ending characters:
<>. All other characters
* are available as unbracketed delimiters.
So your example could be written as
$foo = qq(12."bar bar bar"|three);
$foo =~ s/^(12[.])/$1../;
the ^ means match at the start of the sting, the
() means capture this text to the variable
12 just matches the string
"12", and the
 mean match any one of the characters inside the brackets. The brackets are being used because
. has special meaning in regexes in general, but not inside a character class (the
). Another option to the character class is to escape the special meaning of
\, but many people find that to be uglier than the character class.
$foo =~ s/^(12\.)/$1../;
Another way to insert text into a string is to assign the value to a call to
substr. This highlights one of Perl's fairly unique features: many of its functions can act as lvalues. That is they can be treated like variables.
substr($foo, 3, 0) = "..";
Here is a fully functional Perl script that contains the code above.
#!/usr/bin/perl use strict; use warnings; my $foo = my $bar = qq(12."bar bar bar"|three); $foo =~ s/(12[.])/$1../; my $i = index($bar, "12.") + length "12."; substr($bar, $i, 0) = ".."; print "foo is $foo\nbar is $bar\n";
* all characters except whitespace characters (space, tab, carriage return, line feed, vertical tab, and formfeed) that is