Bash Regular expression replace (regexp)
You can easily use bash to search-and-replace on variables…
f="/home/alice/myfile.md"
$ echo ${f//.md/.pdf}
/home/alice/myfile.pdf
$ echo ${f//alicee/bob}
/home/alice/myfile.md
$ echo ${f////-}
-home-alice-myfile.md
Splinch[/caption]