Yes. You just need to loop over the characters in C. Eg:

#! perl -slw
use strict;
use Inline C => Config => BUILD_NOISY => 1;
use Inline C => <<'END_C',  NAME => 'junk1_IC', CLEAN_AFTER_BUILD => 0
+;

void decrypt( char *e, char *key ) {
    while( *e ) *e++ = *e ^ *key++;
    return;
}

SV *testit( SV *e, SV *key ) {
    SV *r = newSVsv( e );
    decrypt( SvPVX( r ), SvPVX( key ) );
    return r;
}

END_C
use List::Util qw[ shuffle ];
use Data::Dump qw [ pp ];
use constant KEY => join'', shuffle map chr, 0 .. 255;

my $source = 'the quick brown fox jumps over the lazy dog';
my $encrypted = $source ^ substr( KEY, 0, length( $source ) );
print "Encrypted:[$encrypted]";

my $decrypted = testit( $encrypted, KEY );
print "Decrypted:[$decrypted]";

__END__
C:\test>1172052.pl
Encrypted:[Ù?Â→┬ßÁÀFBQÏnå 8üõø♣ÆÄãk­i↨üÿtë½�
+�↨♠,♫õ"æ↓oó]
Decrypted:[the quick brown fox jumps over the lazy dog]
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