Letter to Letter Translations

The s/// operator is great for simple one-to one changes. Sometimes, you mall want to do a many-to-many change, such as translating uppercase letters lowercase letters. For this, you can use the tr /// operator,

The tr/// operator lets you specify individual letters, or range of letters with a hyphen (-). For example, you can use the following to change the case of the uppercase letters in $Test:

$Test =~ tr/A-Z/a-z/;

The tr /// operator returns the number of changes that it makes. It also has some modifiers that are quite different than those for m// and ///.

The tr /// operator does not use regular expressions, only actual characters and character ranges.

Modifiers for tr ///

c - Complement of the first argument is used
d - Deletes matching characters that are nor replaced
s - Removes duplicate replace characters

The modifier is useful to keep the list of characters between the first and second slash short. For example, if you want to change all characters other than digits into linefeeds, you could use

$Test =~ tr/0-9^n/c,- # Note that "c" to invert range

The d modifier allows you to delete instead of replacing certain charcters. For example, if you want to delete all the nondigits, you would use

$Test =~ tr/0-9//cd; # Change non-digits into nothing

The s modifier is useful for collapsing duplicate characters. It causes Perl to treat all the found characters as one before doing the translation. For example, you may want to change all instances of two or more adjacent commas into just one comma:

$Test =~ tr/,/,/s;

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