It could be interesting to know how you are sending "Ctrl+C". Also, I can't figure how you came that Ctrl+C is the same as '\x03'.
If you 'open' a shell process and send '\x03' it won't be interpreted as Ctrl+C but as chr(3):

$ perl -e 'open F, "|cat>test" or die("cant open"); print F "\x03"; cl
+ose F'
$ hexdump -C test
00000000  03                                                |.|
00000001
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However If you mean pressing 'Ctrl+C' the shell will send a signal (nothing to do with values) that you can trap as Athanasius said before.

$ perl -e '$SIG{INT} = sub { die "Got signal" }; while() {};'
[Press CTRL+C]
Got signal at -e line 1.
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