slow fileutil::foreachLine

I have this function:

proc ws::get_words {wordfile} {
    set in [open $wordfile r]
    try {
        while {[gets $in line] >= 0} {
            if {[regexp {^[a-z]+$} $line matched]} {
                lappend ::ws::Words [string tolower $matched]
            }
        }
    } finally {
        close $in
    }
}

It reads about 100_000 lines and ends up keeping about 65_000 of them
(from /usr/share/dict/words)

I tried replacing it with:

proc ws::get_words {wordfile} {
    ::fileutil::foreachLine line $wordfile {
        if {[regexp {^[a-z]+$} $line matched]} {
            lappend ::ws::Words [string tolower $matched]
        }
    }
}

The first version loads "instantly"; but the second version (with
foreachLine) takes seconds.

I'm using Tcl/Tk 9.0b2