Manipulate regex variable after a pattern match

Search Regex expression is:

_(01|02|03|04)_

Replac开发者_如何学Goe expression is:

_$1_

Result is:

_01_/_02_/_03_/_04_ (depending on the match)

How do I manipulate the variable so it strips away the 0 to return a single digit:

_1_/_2_/_3_/_4_

?

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Make the match be: 0(1|2|3|4) and the replacement be $1.