It's possible to use unicode characters as delimiters (with utf8), but Perl doesn't recognise pairs in such a case, and the behaviour of substitution depends on Perl version:

~$ perl5.20.1 -Mutf8 -wE 'say "abc" =~ s’b’x’r'
axc
~$ perl5.18.1 -Mutf8 -wE 'say "abc" =~ s’b’x’r'
Substitution replacement not terminated at -e line 1.
[$?: 255]
~$ perl5.18.1 -Mutf8 -wE 'say "abc" =~ s’b’’x’r'
axc
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($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
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