tcl regsub bug

 1 tcl>set drv  5
 2 tcl>set foo  "oai21_e5m_hvt"
 3 tcl>regsub {_(_v\d)?e(\d+)}  $foo  "_ \1 e$drv" goo
 4  1
 5 tcl>echo $goo
 6 oai21_e5m_hvt
 7 tcl>echo $foo
 8 oai21_e5m_hvt
 9 tcl> string  match $foo $goo
10  0
11 tcl>string  length $foo
12  13
13 tcl>string  length $goo
14  14
15 tcl>string  index $goo  6
16
17 tcl>string  index $foo  6
18 e
19 tcl>

Reason:

the problem is that because of the 's the \1 is being translated into hex 0x01 or the SOH char

they need to \ the \1 or \\1


the following is the right


regsub {_(_v\d)?e(\d+)} $foo "_\\1e$drv" goo