I found at least the location...
This error is thrown in PerlIO_push() in perlio.c: 

PerlIO *
PerlIO_push(pTHX_ PerlIO *f, PERLIO_FUNCS_DECL(*tab), const char *mode
+, SV *arg)
{
    if (tab->fsize != sizeof(PerlIO_funcs)) {
      mismatch:
        Perl_croak(aTHX_ "Layer does not match this perl");
    }
    if (tab->size) {
        PerlIOl *l;
        if (tab->size < sizeof(PerlIOl)) {
            goto mismatch;
        }

[download]

As for the meaning.... dunno. Has an incompatible IO layer been pushed onto $sock (wild guess) ?

In reply to Re: Layer does not match this perl by shmem
in thread Layer does not match this perl by BrowserUk

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