Regular Expression Help

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks
I have this regular expression:

if($filename=~/(\w+)\.(\w{3})/gi){print "\nThis is a match::$filename\
+n"}else{print "\nNOMatch::$filename\n";}
[download]

I need to make sure that the file name has letters or _(underline), but no spaces and followed by a .(dot) and finally the three letters extension, but I can't figure it out the right match to prevent stranger characters entered for the file name, can anyone help on that?
Thanks a lot!

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Re: Regular Expression Help by ikegami (Patriarch) on Jan 06, 2006 at 15:43 UTC
Your missing the anchors, and the /g, the /i and the parens are unnecessary: `/^\w+\.\w{3}$/` [download] But that's not perfect because \w allows for digits, so: `/^[a-zA-Z_]+\.[a-zA-Z_]{3}$/` [download] To allow filenames with no extention or with extentions short than 3 characters: `/^[a-zA-Z_]+(?:\.[a-zA-Z_]{0,3})?$/` [download]	[reply] [d/l] [select]
Re^2: Regular Expression Help by Anonymous Monk on Jan 06, 2006 at 16:32 UTC
One of my problems is not to allow file names without extentions and with no less than 3 characters.	[reply]
Re^3: Regular Expression Help by ikegami (Patriarch) on Jan 06, 2006 at 16:46 UTC
No problem. Just use the second snippet instead of the third one.	[reply]
Re^3: Regular Expression Help by Anonymous Monk on Jan 06, 2006 at 16:48 UTC
How do I say match anything but not allow spaces between words? Like: `if($filename=~/.!\s[.](?!bat$\|exe$).$/gi){...` [download] This is not working if I use .*!\s	[reply] [d/l]
Re^4: Regular Expression Help by thedoe (Monk) on Jan 06, 2006 at 19:11 UTC