Answer by Shawn for When I run a file which is begin with "#!/usr/bin/perl -w", I get a error: "syntax error at line 153, near "=~ ?""

$output_volume =~ ?^([\S]+).mnc?

This used to be valid perl and thus might appear in old code and instructional material.

From perlop:

In the past, the leading m in m?PATTERN? was optional, but omitting it would produce a deprecation warning. As of v5.22.0, omitting it produces a syntax error. If you encounter this construct in older code, you can just add m.