TCL:
bind pub - !hello pub_hello
proc pub_hello {nick host hand chan text} { putmsg $chan "Hello, $nick" }

mIRC Scripting:
on *:TEXT:!hello:#:pub_hello $nick $chan
alias pub_hello { msg $2 Hello, $1 }

• pub: The event which triggers that bind. pub= channel message; msg= private message to the bot; notc = notice .... (See: http://tclhelp.net/eggdrop Chapter 11/A)
  
• -: Necessary access level on the bot for a user to use it. n = owner, m = master, |m = channel master, o|o = global op or channel op, - = everyone (but ignored users <- defined by config)
  
• !hello: The command. Does not support wildcards when using type "pub".
  
• pub_hello: The procedure name to trigger. Be careful not to overwrite tcl's defaults (join, ...)
  
• putmsg $chan "Hello, $nick": The code for it. putmsg sends a message to a channel/nickname. You need quotes around the text!
  
• {nick host hand chan text}: The variable names for arguments... in mIRC Scripting those are static $nick $chan $1- ... you cannot change them. In TCL you have to define them. first one contains the nickname, second one the host... you can look that up for all different bind types on http://tclhelp.net/eggdrop (Chapter 11/A) - try to find out for "bind msg" and check, if you could change that procedure for /msg bot !hello