[TxMt] Snippet’s $variables in RegExp

Hi, I’m trying to use ${5:helper text} variable in my regular expression later in the code:

${5/(e)|(.*)/(?1:\te.preventDefault();\n)(?2:)/}})

What I do here? I check if $5 equals "e" and if it does, I append ".preventDefault();" to my "e". But I’d like to write something like this:

${5/($5)|(.*)/(?1:\t$5.preventDefault();\n)(?2:)/}})

Which simply means I’d like users to be able to change "e" into, for example "event".

My whole snippet, for better understanding:

bind('${1:event name}'${2:, ${3:passed object}}, function(${4:e}) { ${0:$TM_SELECTED_TEXT} ${4/(e)|(.*)/(?1:\t/$4.preventDefault();\n)(?2:)/}})