Your regular expression doesn't do what you think it does (I think!). The alternation meta-character | works on the two entities directly next to it. You need to use parentheses with your alternation, maybe like this: 
$text =~ s/(\bArmy\b)|(U\.S\. Army)/US-Army/g;

[download]
 Update: Arghh! Completely disregard. Alternation extends further than I said unless you limit it with parentheses. I seem to be living in opposite land today.

... but it is cleaner to "factor out" the "Army" string and do something similar to: 
$text =~ s/(U\.S\.)?\bArmy/US-Army/g;

[download]
Note: completely untested!

Hope this helps.

In reply to Re: Regexp dashes at boundaries by crashtest
in thread Regexp dashes at boundaries by cormanaz

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