That's probably the simplest and most useful advice - try out the bits of code in the small if you have any questions what they do.   Whether in small test jig programs, in the debugger or typed-in on the command line, just try it out.  

What does .*? mean? Try it with and without the '?'   (pardon the Windows quoting):

perl -e " printf \"'%s'\n\", join \"', '\",  '...tangled web was woven
+...'=~m/(.*?w)/  ;"
'...tangled w'

perl -e " printf \"'%s'\n\", join \"', '\",  '...tangled web was woven
+...'=~m/(.*w)/  ;"
'...tangled web was w'
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And even when you don't understand it, at least you'll know what it did ...