Batch renaming in Terminal (e.g. bash) using RegEx

gistfile1.txt

// Example: replace every capital letter with 'abc', only changing m4a-files
for file in *.m4a ; do mv -vf "$file" "`echo $file | sed -E 's/[A-Z]/abc/g'`" ; done

// Sublime-Text snippet:
<snippet>
	<content><![CDATA[
for file in *.${1:m4a} ; do mv -vf "\$file" "`echo \$file | sed -E 's/${2:[A-Z]}/${0:abc}/g'`" ; done
]]></content>
	<!-- Optional: Set a tabTrigger to define how to trigger the snippet -->
	<tabTrigger>rename</tabTrigger>
	<!-- Optional: Set a scope to limit where the snippet will trigger -->
	<!-- <scope>source.python</scope> -->
</snippet>