#!/usr/bin/tcl
#
# Replace string with another string -OR- include
# only lines successfully modified with a regular
# expression.
#
fconfigure stdout -translation binary -encoding binary
fconfigure stderr -translation binary -encoding binary
set mode [string tolower [lindex $argv 0]]
set from [lindex $argv 1]
set to [lindex $argv 2]
if {-1 == [lsearch -exact [list exact regsub include] $mode]} {exit 1}
if {[string length $from]==0} {exit 2}
while {![eof stdin]} {
 set line [gets stdin]
 if {[eof stdin]} break
 switch -exact $mode {
 exact {set line [string map [list $from $to] $line]}
 regsub {regsub -all -- $from $line $to line}
 include {if {[regsub -all -- $from $line $to line]==0} continue}
 }
 puts stdout $line
}