Custom perl to paste X CLIPBOARD stopped working

[rxvt-unicode at catcons.co.uk]

Hello :-)

A custom perl script for hotkey pasting X CLIPBOARD into urxvt stopped
working.  I am not aware of any system change that coincided with the
breakage, despite keeping logs and using paste in urxvt very frequently.

~/.Xresources includes:

URxvt.keysym.Mod4-v: perl:clipboard:paste 
URxvt.perl-ext-common: default,matcher,clipboard

/usr/lib64/urxvt/perl/clipboard is:

#! perl 
sub on_sel_grab { 
    my $query = $_[0]->selection; 
    open (my $pipe,'| /usr/bin/xclip -in -selection clipboard') or die; 
    print $pipe $query; 
    close $pipe; 
} 
sub paste { 
    my ($self) = @_; 
    my $content = `/usr/bin/xclip -loop 1 -out -selection clipboard` ; 
    $self->tt_write ($content); 
} 
sub on_user_command { 
    my ($self, $cmd) = @_; 
    if ($cmd eq "clipboard:paste") { 
        $self->paste; 
    } 
} 

The xclip command works at the command prompt.  The script's file size and
permissions are the same as when it was installed.  I added logging to the
script, for example in the paste sub:

open(my $logfh, '>>/tmp/urxvt_paste.log') ; 
print $logfh "paste: running\n";

No logs appeared.  I ran urxvt by:

URXVT_PERL_VERBOSITY=11 urxvt -pe clipboard & 

The trace included:

urxvt: loading extension '/usr/lib64/urxvt/perl/clipboard' into package
'urxvt::ext::clipboard'
[used Super+V]
urxvt: USER_COMMAND (urxvt::term=HASH(0x8bfef8), clipboard:paste ) 
urxvt: USER_COMMAND returning <>

It seemed the custom perl script's sub was being called but was not
effective.  urxvt 9.10 was removed and re-installed.  Same.

A "hello world" perl script worked.

Experimenting, I changed the shebang line in /usr/lib64/urxvt/perl/clipboard
to:

#! /usr/bin/perl    
 
and tested again.  The logs appeared for subs on_user_command and
on_sel_grab but the on_user_command log did not show the "if ($cmd eq
"clipboard:paste")" test passed.

What can I try now?

Best

Charles