shmem [qurx] ~ > perl -CO use Encode qw/ _utf8_on /; use Devel::Peek; $s = " "; _utf8_on( $s ); substr $s, 0, 1, "\x{b5}"; Dump $s; print length $s, $/; print "\$s: '$s'\n"; __END__ SV = PVMG(0xf64ff0) at 0xedd8c8 REFCNT = 1 FLAGS = (SMG,POK,pPOK,UTF8) IV = 0 NV = 0 PV = 0xee2620 "\302\265"\0 [UTF8 "\x{b5}"] CUR = 2 LEN = 10 MAGIC = 0xf66010 MG_VIRTUAL = &PL_vtbl_utf8 MG_TYPE = PERL_MAGIC_utf8(w) MG_LEN = -1 1 $s: 'µ'