That's not what happens under Win7, perl 5.16, and the latest AS 5.16-repository version of Scalar::Util (with quotes adjusted for MS pleasure):

C:\>perl -MScalar::Util=looks_like_number -e "print looks_like_number 
+'Inf'"
20
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Oh. OK, if you say so. But why did the output ne 'True' (unless 'Inf/INF/inf' is treated as NAN?
Just then, though, a lightbulb flashed on -- AhHA,   /me said to myself!     RTFM!

looks_like_number EXPR
Returns true if perl thinks EXPR is a number. See "looks_like_number" 
+in perlapi.
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Unfortunately, the link, <a href="/perldoc?perlapi#looks_like_number" class="podlinkpod">&#34;looks_like_number&#34; in perlapi</a> (to which 'See' directs us) is broken.

So forging blindly onward with what seemed, OTTOMH, some semi-plausible alternatives:

C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber 'Inf'"
20
C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber 'foo'"
0
C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber 'inf'"
20
C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber '7'"
1
C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber '7874321907'"
2
C:\>perl -e "use Scalar::Util(looks_like_number); print looks_like_num
+ber(7874321907)"
8704
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It all leaves me deep in 'WTF' territory and slipping into the quicksand.

So prithee, Wiser heads: Prevail! and halp, hal blubh blub o o ....

Update: added first 1.5 sentences after the first blockquoted code.