The example scenario uses a regex string to match the dialing of international calls. The string matches calls prefixed with either + or 00 (the UK dialing prefix for international calls).
The regex string used was: ^(\+|00)(.+)$
The string works as follows:
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The ^ matches the start of the string.
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The ( ) brackets group elements for processing and, potentially for future digit translations.
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The first pair of brackets contain \+|00:
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The \+ matches a literal + character (the E.164 international prefix indicator). The string needs a \ as a + on its own is a regex command.
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The | separates different possible matches.
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Therefore, the first pair of brackets matches any numbers beginning with a + or 00.
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The second pair of brackets contains .+:
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The . matches any digit or character.
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The + modifies the preceding . to match any number of matches.
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Therefore, the .+ operate together to match any number of digits and characters.
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The second pair of brackets enclose the match for any number of characters. In this example, a translation can use the value $2 to refer to the matched characters, without their + or 00 prefix.
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The $ matches the end of the string.
