/usr/lib/gnu-smalltalk/vfs/utar is in gnu-smalltalk 3.2.5-1+b3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 | #!/bin/sh
#
# Written by Paolo Bonzini 2002
# bonzini@gnu.org
# (C) 2002 The Free Software Foundation.
#
#
uni_cat ()
# $1 is the archive name
{
    case "$1" in
    *.tar.Z)	compress -dc "$1"
	;;
    *.tar.gz)	gzip -dc "$1"
	;;
    *.tar.bz2)	bzip2 -dc "$1"
	;;
    *.tar)	cat "$1"
	;;
    *.tgz)	gzip -dc "$1"
	;;
    *.tbz)	bzip2 -dc "$1"
	;;
    *)		echo "unknown extension"
    esac
}
mctarfs_list ()
# $1 is the archive name
{
    uni_cat "$1" | tar tvf - | gawk '
	{
	    y = substr($4, 1, 4)
	    m = substr($4, 6, 2)
	    d = substr($4, 9, 2)
	    mm = substr("JanFebMarAprMayJunJulSepOctNovDec", m*3-2,3)
	    $4 = mm " " d " " y
	    $2 = "1 " substr($2, 1, index($2, "/")-1) " " substr($2, index($2, "/")+1)
	    print
	}'
}
mctarfs_copyout ()
# $1 is the archive name
# $2 is a name of a file within the archive
# $3 is a name of a file within the system (to add from or extract to)
{
    TMPDIR=/tmp/mctmpdir.$$
# FIXME: Try harder to generate a unique directory if this fails
    mkdir -m 0700 $TMPDIR || exit 1
    cd $TMPDIR
    uni_cat "$1" | tar xvf - "$2" 2>/dev/null
    mv "$2" "$3"
    cd /
    rm -rf $TMPDIR
}
#
# main
#
    umask 077
    case "$1" in
    list)   mctarfs_list $2
	    exit 0
	    ;;
    copyout) mctarfs_copyout $2 $3 $4
	    exit 0
	    ;;
    esac
    exit 1
 |