Once again thankyou. That does greatly simplify the code and produce the desired results: 

SV* test( SV *a, SV *b ) {
    if( SvREADONLY( a ) )
        a = newSVpv( SvPVX( a ), 0 );
    else
       SvREFCNT_inc( a );

    if( !SvOK( a ) )
        sv_setpvn( a, "", 0 );

    sv_catsv( a, b );
    return a;
}

...
__END__
c:\test>test
billfred
fred
billfred
1fred
1fred1

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^6: XS/Inline::C concat *any* two SVs. by BrowserUk
in thread XS/Inline::C concat *any* two SVs. by BrowserUk

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